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Aux Talk

Perhaps the most versatile track type in Pro Tools is one that you can't even record to!

In last month's column, we looked at the track types that actually hold audio or MIDI recordings in Pro Tools sessions: audio, MIDI and Instrument tracks. However, there are also some very important track types which don't themselves contain recorded material, so let's continue by looking at possibly the most versatile track type: the Aux (auxiliary input) track.

Aux tracks enable a user to route live audio through Pro Tools. In many ways they work just the same as an audio track, except that you cannot record any audio on Aux tracks. Their applications are many and varied, and include:

Submixing a group of tracks. For example, all the elements of a multitracked drum kit could be routed to an Aux track to create a stereo drum mix with a single fader to adjust its level.

Bringing audio into Pro Tools from hardware synths and drum machines that are being triggered live from Pro Tools MIDI tracks (although it's often neater to use an Instrument track for this).

Setting up auxiliary effects such as reverbs and delays for send/return use.

Routing the returns from external hardware effects back into Pro Tools.

Routing hardware audio devices such as CD players, record decks or an external audio mixer.

Creating headphone mixes for performers.

Managing additional outputs from multitimbral software synths that are hosted on an Instrument track.

Screen 1 shows a drum kit recording in Pro Tools. What we need to do is create a subgroup for the entire kit, so that we can use the fader on the subgroup channel to adjust the overall level of the drum kit in the mix. First, we need to create a stereo Aux track. Highlight the track next to where you want to insert the new track — in this case the 'OHs' track. Now go into the Track menu and select New…, or hit Command+Shift+N (Windows: Ctrl+Shift+N). Choose one stereo Aux Input track from the New Tracks menu and click OK. Pro Tools will add an Aux track to the right of the selected track. Double-click on the Aux Input track name and rename it to 'Kit Sub'.

Screen 1: In this Pro Tools session, I have a standard multitracked drum kit recording.Now we need to set up the routing so that all the drum kit tracks will go through the Kit Sub channel. What we need to do is route each audio track's output to the same stereo bus, then assign that same bus as the input to the Kit Sub track. You can click on each track's output routing box in turn to do this, but it's quicker to apply the setting to all the tracks at once. First, select all the drum kit tracks by clicking on the first track ('kick'), holding down the Shift key, and clicking on the last drum kit track ('OHs'). Now hold down Shift and Alt together as you change one track's output assignment, and watch as all the selected tracks change to your chosen bus — in this case bus 3/4. (Throughout Pro Tools you'll find that holding down Shift and Alt applies a change to all selected tracks, while holding down Alt applies it to all tracks.)

Next, rename bus 3/4 by right-clicking on one audio track's output box and choosing Rename. Change the name to 'kit sub' from the contextual menu that pops up. Note that renaming it here will change the labelling for bus 3/4 everywhere, not just the selected track. You could go into the Buss tab in the I/O Setup window, but this is much easier.

On the Kit Sub Aux Input track, change the input routing to 'kit sub' and away you go. Now you have a subgroup for all the drum kit tracks. This method allows a mixer to control huge mixes using submixed Aux channels. In effect, hundreds of tracks can be running through half a dozen Aux channels. I often have 50-track mixes running through fewer than 10 submix channels.

So now we have our drum kit subgroup, let's use an Aux Input track to create a reverb for the drums. We want the reverb track to appear between the 'OHs' and 'Kit Sub' channels, so with the 'OHs' track highlighted, create a new stereo Aux Input track. Rename it 'Kit Reverb'. Now highlight all the drum kit tracks, like we did when setting up the routing. Again, hold down Alt and Shift, and this time, click on one of the Sends A-E on one of the tracks and create an Aux Send to a stereo bus (5/6 in my example). An Aux Send to the chosen bus will appear on all the drum kit tracks. Right-click on the bus 5/6 and rename it 'Kit Reverb'.

Next, rename the new Aux track 'Kit Reverb' and then set its input to the bus now labelled 'Kit Reverb'. Insert your preferred reverb into one of the Inserts A-E on the Kit Reverb Aux track — in the example, I've used Exponential Audio's Phoenixverb. Finally, change the Aux A-E Send display to a mini-fader by holding the Command key (Mac) or Ctrl key (Windows) and clicking on the little arrow to the left of the routing name. Now you can adjust the send level from each track into the kit reverb.

One thing you'll notice with the way we have set things up so far is that if you hit the Solo button on any of the drum tracks, you won't hear anything unless you also solo the Kit Sub track; and you won't hear any reverb unless you solo the Kit Reverb track too. This gets pretty tedious, but fortunately, you can switch Pro Tools tracks into 'solo safe' mode by Command-clicking (Windows: Ctrl-clicking)Screen 2: Having applied all the techniques outlined in this article, my drum kit tracks are now routed to a subgroup Aux track called 'Kit Sub', and each of them has sends with mini-faders to a reverb and a headphone mix bus. on their Solo buttons. When a track is in 'solo safe' mode, its output doesn't get muted when other tracks are soloed, so if the Kit Sub track is in this mode, you'll be able to solo the snare or kick without having to also solo the subgroup channel.

Aux Sends and Aux tracks can be used to create secondary mixes that are different from the main mix, which is useful if your performers want to hear a different balance of instruments in their headphone mixes. Follow the same procedure as described in 'Creating A Reverb Return' above, but label everything something like 'cans mix' and set the output routing of the additional Aux Input track to a spare pair of outputs of your interface. Now the Aux Input fader becomes your overall headphone level, and the mini-faders set up the mix that's going to it.

Finally, Aux inputs can be used to route audio from external hardware such as synths and rack gear into Pro Tools. To do this, simply create a new Aux Input track and then select a free hardware input from your hardware interface. Remember you can't record on an Aux track, so if you want to record the input from this channel at any point then you are going to have to either route its output to a new audio track, or create a separate audio track with the same input assignment.

I hope that this two-part workshop has given you an insight into the way that signal flows through the Pro Tools mixer, and how you can set up the different tracks available to you in Pro Tools.

A Master Fader should always be present in a Pro Tools session, no matter how small. With it you can monitor headroom on the output — without a master fader, the output could be clipping and there would be no visual indication that this was happening. From a mixing point of view, a key feature of master faders is that their insert points are post-fader, unlike the insert points on all other track types, which are pre-fader.